go/internal/gccgoimporter: use t.TempDir() in tests
go/internal/gccgoimporter: use t.TempDir() in tests

Use t.TempDir() instead of os.MkdirTemp().

This is a copy of CL 309356 from the main repo.

Updates golang/go#45402.

Change-Id: Ia555a701e4de568871a765ee551e65a5c998cde9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/362246
Trust: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools